Latest news with #AbhijitMajumder
Time of India
2 days ago
- Science
- Time of India
The secret language of touch: Cells align and communicate through mechanical sensing and memory
MUMBAI: We often imagine cells as tiny chemists—receiving signals, processing instructions, and producing proteins in a flurry of biochemical activity. But what if they were also quiet engineers, silently listening to the architecture around them, tuning in to tensions that stretch and pull, feeling their way into place? A new study from researchers at the Indian Institute of Technology (IIT) Bombay suggests exactly that: that cells don't just see or hear—they feel. And more remarkably, they remember. In a soft, silent laboratory, without a single shout of a chemical signal, muscle precursor cells learned to align themselves by sensing an invisible tension underfoot. The finding, published in *Cell Reports Physical Science*, offers a rare and elegant peek into the physical intelligence of life—and was just chosen as among the journal's best work in biophysics. It's easy to overlook the poetry in biology. But consider this: the cells in our muscles lie in perfect parallel, allowing them to pull in unison. The ones in our eyes form radial fans that help focus light to a point. Blood vessels curve gracefully toward wounds. Such arrangements are not decorative. They're essential. Form begets function. But how do cells know where to go? Who—or what—is guiding them? 'We've long assumed it's all chemistry,' says Prof. Abhijit Majumder, who led the study. 'That cells respond to growth factors, to gradients, to instructions carried by molecules.' That assumption held for decades. But in recent years, a quiet revolution has been unfolding in the study of mechanobiology—where mechanical forces, not chemicals, do the talking. Cells, it turns out, are tactile creatures. They feel how soft or stiff their surroundings are. They respond to being stretched, compressed, or nudged. They even react to textures far smaller than themselves. 'In real tissue, there's always some mechanical inhomogeneity,' explains Prof. Majumder. 'Whether it's a growing organ, a wound in repair, or even a tumour—there's tension. The question is, how do cells respond?' To explore this, the IIT Bombay team created a miniature world—a soft gel made of polyacrylamide, inside which they embedded a single glass bead. Imagine a soft mattress with a marble tucked inside. Now place it in water. As the gel swells, the bead resists. The area around it stretches unevenly, creating a gentle strain gradient—an invisible field of mechanical instruction. Next, they introduced muscle precursor cells—myoblasts—on top of this landscape. What followed was extraordinary. The cells nearest the bead began to align themselves, fanning out radially like sunrays. Not due to gravity or light or nutrients. Simply because they felt the difference in stretch beneath them. 'It was as though they sensed the lay of the land—the pre-strain in the gel,' says Dr. Akshada Khadpekar, the lead author. 'And not only did they align, they passed the message outward, organising others farther away.' The effect stretched across a span of 1–2 millimetres—roughly 20 to 40 cell lengths. On gels without a bead, the alignment barely extended 0.35 mm. To ensure this wasn't due to chemical cues, the researchers ran control experiments. They swapped out extracellular matrix (ECM) proteins, adjusted the stiffness of the gels, and played with surface coatings. Only the softness of the substrate—and the presence of that gentle pre-strain—made the difference. 'This ruled out biochemical factors. The alignment was purely mechanical,' confirms Dr. Khadpekar. But how do you prove what you can't see? That's where collaboration came in. Prof Parag Tandaiya from IIT Bombay's Mechanical Engineering department joined the team to run finite element simulations—computer models that mapped the stress and strain in the gel. The simulations confirmed what the eye could not: the invisible forces the cells were feeling closely matched the patterns of alignment observed. 'This was key,' says Prof. Tandaiya. 'There's no experimental way to directly measure these subtle strain fields. Simulations let us visualise what the cells themselves are sensing.' To test how universal this effect was, the team didn't stop at one bead. They tried hollow capillaries, bead arrays, and combinations of both. The cells aligned not just in straight lines but in arcs, spirals, and waves—shaped by invisible gradients of tension. Different cell types behaved differently depending on how stretched out they were, or how forcefully they tugged on the surface. 'What's truly fascinating,' says Prof Majumder, 'is that cells don't just respond to strain. They respond to strain direction. They align themselves along the path of greatest stretch, like grass flattening in the wind.' The researchers then used this insight to build a predictive model. By factoring in a cell's shape, contractile strength, and the stiffness of the substrate, they could estimate how it would align. A mechanical fortune-teller of sorts—reading the future from the pull of a gel. But the implications are far from academic. In tissue engineering, such findings could allow scientists to shape cell patterns not with chemical scaffolds but with simple, passive designs. In cancer biology, understanding how tumours distort their mechanical environment could help explain how they influence nearby cells. And in regenerative medicine, tweaking the mechanical properties of ageing or injured tissue might help restore normal function. The beauty of this study lies in its simplicity. No expensive chemicals. No fancy equipment. Just a soft gel, a glass bead, and a curious question: What if cells could feel? They can. And they do. 'It's a very intelligent response,' says Prof. Tandaiya. 'One that we're only beginning to understand.' For now, though, the findings sit like ripples on the surface of science—quiet but far-reaching. Because every now and then, in the stillness of a lab, we discover that life has its own sense of touch. And sometimes, that's enough to show it the way.
The Hindu
3 days ago
- Health
- The Hindu
IIT Bombay researchers uncover the role of invisible mechanical cues in tissue organisation
In a new study, scientists at the Indian Institute of Technology (IIT) Bombay have demonstrated how cells can sense and respond to invisible mechanical patterns—like built-in tensions around them. The research led by Professor Abhijit Majumder, was published in Cell Reports Physical Science. The findings not only add to the fundamental understanding of how cells organise themselves, but also have important implications for tissue engineering, cancer research, and wound healing. Cells follow very specific patterns, for instance, muscle fibres are aligned parallel to each other to enable coordinated movements, blood vessels extend toward wounds to facilitate healing, and cells in the eye are arranged radially to help focus light precisely onto the retina, ensuring clear and accurate vision. Such precise spatial organisation is essential for proper tissue function. The arrangement of cells directly influences how effectively a tissue can carry out its role, be it contracting, transporting nutrients, or processing sensory input. But how do cells determine their correct location and orientation within these complex systems? Professor Majumder said that for decades, scientists believed that cells primarily relied on chemical signals, like growth factors or morphogens, to decide how and in which direction to grow. 'However, recent discoveries in this field suggest that mechanical signals are just as important. Cells can feel how stiff their surroundings are, detect tiny stretches, and even respond to surface textures smaller than themselves. In living tissue, mechanical inhomogeneities are common. You see it in tumours, healing wounds, and developing organs. But we haven't fully explored how cells interpret and respond to these physical cues,' Professor Majumder said. The researchers embedded a rigid object inside an otherwise soft material, mimicking mechanical inhomogeneity. The goal was to mimic how tissues naturally develop internal tension during processes like growth, injury, or tumour formation, and how cells might sense and respond to such forces. Lead author Dr. Akshada Khadpekar explained, 'To simulate these conditions, we designed a soft polyacrylamide hydrogel with a small, rigid glass bead embedded inside. This setup replicates a rigid structure surrounded by softer material, like a tumour within the body tissue.' When the gel was placed in water, it began to swell everywhere except where the bead was, because the stiff bead resisted the expansion. This created a pre-strain gradient— a varying stretch pattern around the bead. When muscle precursor cells were added to the gel, the pre-strain gradient played a crucial role in guiding their alignment. 'Cells near the bead detected the pre-strain gradient and aligned radially. As they exerted forces on the substrate, the mechanical signal propagated outward. This alignment extends about 1–2 mm (20–40 cell lengths) from the bead, reinforcing long-range organisation,' Dr. Khadpekar said. On a soft, uniform gel without a bead, however, the alignment was limited to about 0.35 mm. Professor Majumder added, 'Think of it like a shallow crater around the bead. But instead of falling in, the cells sense the stretching pre-strain and align accordingly.' To be sure this wasn't due to chemical factors, the researchers ran control experiments. They changed the type of extracellular matrix (ECM) proteins used to coat the gel and varied the stiffness of the substrate. Only on soft gels did the cells align. Harder gels masked the effect, and altering the ECM had no impact, proving that the alignment was not biochemical in origin. To further investigate the mechanism behind cell alignment, the research team collaborated with Professor Parag Tandaiya from the Department of Mechanical Engineering at IIT Bombay and employed finite element simulations to model the mechanical environment created by the swelling hydrogel. These computational models confirmed that the strain fields generated in the gel closely matched the patterns of cell alignment observed in experimental conditions. 'This was crucial because there's no direct way to measure these subtle internal pre-strain fields experimentally. Without simulations, we wouldn't have been able to formulate or test our hypothesis about what the cells were sensing,' Professor Tandaiya said. To test the generality of this phenomenon, the researchers extended their experiments beyond individual spherical beads to hollow glass capillaries, glass beads, and their combinations. In all cases, the cells aligned along invisible force patterns, forming arcs, waves, or spirals. The researchers also tested different types of cells and found that how the cells aligned depended on how much force they could apply and how stretched out they were. 'The cells don't just sense stretching of their substrate, they seem to also detect the direction in which the substrate is stretched the most and they line up in that direction. It's a very precise and intelligent response, and we believe this is the first time such behavior has been observed in this way,' Professor Tandaiya added. Using these findings, a model was created to predict which cells would align based on their shape, strength, and stiffness of the surface. This discovery has significant implications across multiple fields. 'In tissue engineering, we might guide cell organisation just by shaping soft materials, without complex scaffolds or stimulation. Or in cancer, the stiffness of tumours could explain how they influence nearby cells. And in regenerative medicine, adjusting tissue stiffness may help restore healthy cell patterns in aging or damaged tissues,' Dr. Khadpekar said.
